Theoretical considerations in an approximate method for estimating the blade performance of a Darrieus-type cross-flow water turbine.

Furukawa, Akinori; Takamatsu, Yasuo; Takenouchi, Kazuki

doi:10.1299/kikaib.53.2507

Cited by 6 publications

(11 citation statements)

References 0 publications

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“…In this study, the blade sections are assumed to be symmetrical NACA 0018 airfoil for BEM calculations. However, to account for flow curvature effects [12], blade sections obtained by conformal mapping [13] of NACA 0018 airfoil to the curvilinear flow along the blade path are assumed in CFD analysis. That is, the present study assumes that the results of BEM calculation using symmetrical airfoil data correspond to the performance of a wind turbine rotor with cambered blades as obtained by transformation of the symmetrical airfoil to an equivalent curvilinear flow field.…”

Section: Quadruple-multiple Streamtube Modelmentioning

confidence: 99%

Predicting Double-Blade Vertical Axis Wind Turbine Performance by a Quadruple-Multiple Streamtube Model

Hara¹,

Kawamura²,

Akimoto³

et al. 2014

International Journal of Fluid Machinery and Systems

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Double-blade vertical axis wind turbines (DB-VAWTs) can improve the self-starting performance of lift-driven VAWTs. We here propose the quadruple-multiple streamtube model (QMS), based on the blade element momentum (BEM) theory, for simulating DB-VAWT performance. Model validity is investigated by comparison to computational fluid dynamics (CFD) prediction for two kinds of two-dimensional DB-VAWT rotors for two rotor scales with three inner-outer radius ratios: 0.25, 0.5, and 0.75. The BEM-QMS model does not consider the effects of an inner rotor on the flow speed in the upwind half of the rotor, so we introduce a correction factor for this flow speed. The maximum power coefficient predicted by the modified BEM-QMS model for a DB-VAWT is thus closer to the CFD prediction.

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Section: Quadruple-multiple Streamtube Modelmentioning

confidence: 99%

Predicting Double-Blade Vertical Axis Wind Turbine Performance by a Quadruple-Multiple Streamtube Model

Hara¹,

Kawamura²,

Akimoto³

et al. 2014

International Journal of Fluid Machinery and Systems

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“…theoretical curves to the experimental data was assumed to indirectly include flow curvature effects (Migliore et al, 1980) in addition to generator efficiency. However, in the present paper, the theoretical curves are directly modified in relation to the virtual incidence (angle of attack) using conformal mapping (Furukawa et al, 1990;Akimoto et al, 2013). After modification, the upstream velocity is multiplied by a factor independent of the tip speed ratio, as the parameter of fitting.…”

Section: Resultsmentioning

confidence: 99%

“…Fitting curves to experimental data using the theoretical model shown in previous papers (Hara et al, 2014c(Hara et al, , 2014d are replaced with new fitting curves modified by virtual incidence based on flow curvature effects (Migliore et al, 1980;Furukawa et al, 1990;Akimoto et al, 2013). Variations in the vorticity field around circular blades, relating to differences in the tip speed ratio, are described in detail using results of CFD analysis.…”

Section: Introductionmentioning

confidence: 99%

Experiment and numerical simulation of an aluminum circular-blade butterfly wind turbine

Hara

Shiozaki

Nishiono

et al. 2016

JFST

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To reduce costs involved in manufacturing small wind turbines, an aluminum circular-blade butterfly wind turbine (ACBBWT) has been developed, in which four blades of the turbine were extruded and bent to shape then attached directly to a rotating flange. The ACBBWT is a vertical axis wind turbine (VAWT) and the rotor diameter of the prototype is 2.06 m. Experiments to obtain the output performance were conducted outdoors using an axial blower; however, the data obtained were rather scattered due to the effects of natural wind. Therefore, performance curves in the high wind speed range are predicted by fitting theoretical curves based on the Blade Element Momentum (BEM) theory, in which modification of virtual incidence due to flow curvature effects is included. Three-dimensional computational fluid dynamics (CFD) analysis of a circular-blade wind turbine model (dia. 2 m) with a shape almost identical to that of the experimental rotor is performed. The results assuming an energy-conversion efficiency of 0.8 agree well with the experimental results at 7 m/s. CFD analysis shows that tip vortices are shed from the top and bottom parts of a circular blade, as with straight-blade VAWTs. However, vorticity in the circular-blade case is lower than that in the straight-blade case, and the cross-section of each tip vortex shed from circular blades appears to be in the shape of a deformed ellipse. In cases of small tip speed ratios, vortex shedding caused by the dynamic stall phenomena is observed around the equator plane in both the downstream and upstream regions, and the vortex shed in the downstream region by a circular blade forms a looped shape. Since distributions of surface pressure and skin friction obtained by 3D-CFD have a similar pattern in both the upstream and downstream regions, which is related to vortex shedding, it is considered that the vortex in the upstream region is likely to also have a looped shape.

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“…Since it is only a geometrical mapping using polar coordinates, the correlation between two flow fields is not clear. Furukawa et al [16] proposed a conformal mapping for explaining the effect of rotation on the performance of vertical axis water turbine. The discussion is on the transformation of flow distribution on the mean line of wing section.…”

Section: Introductionmentioning

confidence: 99%

“…In the present paper, the authors propose a conformal mapping on a complex plane for the bidirectional interpretation between the straight rectilinear and curved flow fields. The main part of the mapping function is mathematically the same as that proposed by Furukawa et al [16]. The function will map the curved flow around the original wing section to the straight flow around a modified wing section with an additional camber.…”

Section: Introductionmentioning

confidence: 99%

A conformal mapping technique to correlate the rotating flow around a wing section of vertical axis wind turbine and an equivalent linear flow around a static wing

Akimoto

Hara

Kawamura³

et al. 2013

Environ. Res. Lett.

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Theoretical considerations in an approximate method for estimating the blade performance of a Darrieus-type cross-flow water turbine.

Cited by 6 publications

References 0 publications

Predicting Double-Blade Vertical Axis Wind Turbine Performance by a Quadruple-Multiple Streamtube Model

Predicting Double-Blade Vertical Axis Wind Turbine Performance by a Quadruple-Multiple Streamtube Model

Experiment and numerical simulation of an aluminum circular-blade butterfly wind turbine

A conformal mapping technique to correlate the rotating flow around a wing section of vertical axis wind turbine and an equivalent linear flow around a static wing

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